1. Field of the Invention
The present invention relates to a tuner, and more particularly to a tuner, in which a printed circuit board is used for substituting a conventional air coil.
2. Description of Related Art
With the development of digital compression technique, global television broadcast system have changed from analog television broadcast system to digital television broadcast system, development of digital broadcast techniques has led to a quick development of the related industry, wherein digital televisions (DTVs) and set-top boxes (STBs) are structural elements of a digital broadcasting system, and a tuner circuit is a key of the DTV and STB or a mobile receiving system.
The tuner is used for amplifying a received radio frequency (RF) signal and descending a frequency of the received RF signal to an intermediate frequency (IF), and then a back-end decoder may decode the received RF signal. A function of the tuner is to select a desired channel and filter the undesired channels, and to avoid an interference exerted on the desired channel by the undesired channels during a frequency descending. Moreover, the received signal is a broadband signal due to carry of multi-channels, and therefore the tuner should have a broadband design, so as to entirely receive and process the received signal.
In the tuner, due to a relatively great frequency bandwidth and differences of the tuner ICs, different bands (VHF-H, VHF-L, UHF) require different impedance matching circuits. Air coils may be applied to a tracking filter, an oscillator, and a signal coupling and impedance matching circuit within a conventional tuner, by which the air coils may be used for adjusting a resonant frequency and an impedance matching.
Since the air coils are relatively large in size, and have to be manually assembled and adjusted during production, production cost is increased due to large size of the components. Meanwhile, excessive manual operation cannot facilitate mass production, and may greatly decrease a throughput and adversely influence the profit and the competitiveness of the product.